1. Field of the Invention
The invention relates to an aluminous sintered refractory product, to a process for manufacturing this refractory product and to a green part, or “preform”, intended to be sintered in order to obtain this refractory product.
2. Description of the Related Art
Among refractories, a distinction may be made between fused-cast products and sintered products.
Unlike sintered products, as described for example in US 2001/0019992 A1, fused-cast products usually comprise an intergranular glassy phase that links the crystallized grains together. The problems posed by sintered products and by fused-cast products, and the technical solutions adopted for solving them, are therefore generally different. A composition developed for manufacturing a fused-cast product cannot therefore a priori be used as such for manufacturing a sintered product, and vice versa.
Sintered products are obtained by mixing appropriate raw materials, then making a green form from this mixture and firing the resulting green form at a temperature and for a time that are sufficient to sinter this green form. This firing may be carried out in firing furnaces or else in situ in the glass furnace for products sold unfired or unfashioned.
Sintered products, depending on their chemical composition and their method of preparation, are intended for a wide variety of industries.
Among sintered products, alumina-zirconia-silica products, commonly called AZS products, and also called aluminous products are used in zones of glass-melting furnaces.
Products such as those described in FR 2 552 756 in the name of Emhart Industries are generally very suitable. Products such as BPAL, ZA33 or ZIRAL, which are produced and sold by Saint-Gobain SefPro, are also particularly well suited and very widely used at the present time. However, with certain recent glass compositions, the formation of bubbles has been observed. These bubbles are generated upon contact with the refractories that make up the furnace and are then trapped in the glass, giving rise to unacceptable defects.
There is therefore a need for a sintered product that gives rise to reduced bubbling effect and that can be used in glass furnaces. The aim of the present invention is to satisfy this need.